Hi Morgan, On Mon, Jul 30, 2007 at 12:04:51PM +0200, Morgan T?rvolt wrote: [...] > your real problem is not the quality part of this equation really. It > is the fact that all drivers implement this differently. A level of > 0x2a35 on snr could mean perfect signal on one driver, and no > reception at all on a second driver. Some cards dont even give you > snr, maybe even a hardware constraint. Actually this will be different > from card to card as well (with the same frontend), given that there > is a different sensitivity on the tuner. Getting this right is really > a very difficult task right now, unless I am totally off here. thank you for the excellent summary! However, I have one thing: the SNR value is only dependent on the demodulator you use, so even with a different frontend, the values can be directly compared as long as you use the same demodulator IC (and firmware, maybe...). For most demodulators, you can give a (more or less) simple equation to calculate the S/N (or C/N, whatever you want to call it) from the register values, but unfortunately there are some exceptions: STV0297 DVB-C for example. The signal strength, in turn, is most often not even useful when comparing devices of the same type - the tolerances are too big, you can only get a rough idea of "any signal present" or "no signal present". (Which is, BTW, sometimes very nice too have, too.) > -Morgan- Regards, Wolfgang _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
